Plug and Play (PnP) technology is an architecture designed and developed by Microsoft Corporation and various independent hardware and software vendors that facilitates the integration of peripheral devices, such as printers, scanners, card readers, etc., into a personal computer system. First introduced with Windows® 95, PnP peripheral devices are configured to identify themselves to the computer system to which they are attached. A PnP compatible operating system receives identifying information and uses it to automatically locate and load a peripheral device driver that is either provided by the user or retrieved from a driver library stored at a location accessible by the computer. Loading the peripheral device driver—also referred to as installing the peripheral device—includes defining an input/output (I/O) queue that is used to queue output to the peripheral device and/or receive input from the peripheral device. The installation is completed without requiring significant user interaction.
Before PnP technology was developed, a system user was required to install a peripheral device manually each time such a device was connected to the system. Manual installation of peripheral device drivers was a burdensome and time-consuming task for the user. It required the user to notify the operating system that the user had connected a peripheral device to the system. The user then had to locate and identify a peripheral device driver for the peripheral device, notify the system of the location of the peripheral device driver and identify an I/O port of the computer to which the peripheral device was attached so that the operating system could redirect an I/O queue for the device to the I/O port. The advent of PnP technology relieved the user from the burdens associated with manually installing peripheral device.
Although PnP technology has facilitated installation of peripheral devices by users with little or no knowledge of computer hardware or software operations, similar technology does not exist for systems in which multiple users simultaneously share the computing resources of a single machine. In such a scenario, client machines are connected to a server computer using a network. The client machines can be standalone computers or terminals. A terminal does not have the processing capability of a computer, but it does have the ability to utilize the processor in the server to execute applications and to provide a user interface for I/O operations.
A server in this environment typically has an operating system that can run several client sessions concurrently. Each client user has access to resources of the server, including the processor, data storage, application programs, etc. Software applications that are resident on the server are available to each client for independent execution by the client. Each session is independent from other clients connected to the server and, therefore, one client cannot access information relating to another client. In this manner, the server provides a logically independent machine for each client connected to the server.
Client users frequently connect peripheral devices to the client computers. For example, a client user may wish to connect a printer to the user's client computer (a “local” printer) to print data generated by an application that is running on the server computer. To do this, the user must manually install the local printer as described above and redirect the printer queue created by the server to the I/O port of the client computer to which the printer is connected. As previously stated, manual installation of peripheral devices is undesirable because it requires significant time and effort on the part of the user.